Data Over Cable Interface Specification (DOCSIS) is one standard among many others that are moving toward modular systems (e.g. modular cable modem termination system (MCMTS)) in order to lower costs. One way to achieve modularity is to separate the DOCSIS media access control (MAC) functionality from the DOCSIS physical layer (PHY) functionality into two different boxes.
Multiple System Operators (MSOs) in the cable space (or any other space) may want to offer higher bandwidth services over different media (other than coaxial cables). For example, the DOCSIS MSOs may want to offer higher bandwidth services through radio frequency over glass (RFoG) or passive optical network (PON). In the latter case, they will need one PHY box for the DOCSIS service and another for the PON service.
MSOs need a special PHY box for every service they want to offer, which may result in many PHY boxes occupying the headend office consuming extra space and power. Having many PHY boxes may result in high cost systems, especially if these different PHY boxes are not fully utilized. Another disadvantage of having many different PHY boxes is the complex management of dealing with many different vendors.
Inefficient use of resources is a major drawback of having different PHY boxes for different services. When using application-specific PHY devices, reusing these boxes for different services may not be feasible. This does not protect the investment that the MSOs make in buying these PHY boxes.
The format of one embodiment of the L2TPv3 packets is shown in FIGS. 3 and 4, where it is shown that the UDP field is optional.
The format of one embodiment of the L2TPv3 data header is shown in FIGS. 5 and 6, where the session ID is provided.
One embodiment of an application (APP) PSP sub-Layer header is shown in FIG. 7, where the same format of this sub-header may be used to support all PHY services
In one embodiment, APP control packet has the format shown in FIG. 8, where the session messages are linked to the control connection through an ID.